Apparatus for and method of treating a web

ABSTRACT

A web is treated, for example dried, by passing it around a rotary cylinder, and deflecting it by air pressure, positive and/or suction, applied to the web immediately adjacent the junction of the web and the cylinder to cause the web to contact a greater portion of the circumferential surface of the cylinder than it would in the absence of the air pressure.

United States Patent [191 Haythornthwaite [451 May 22, 1973 [22] Filed:

[54] APPARATUS FOR AND METHOD OF TREATING A WEB [75] Inventor: JamesHaythornthwnite,

Quebec, Canada [73] Assignee: Scapa Dryers (Canada) Ltd.,

Joliette, Quebec, Canada Sept. 7, 1971 [21] Appl. No.: 178,361

Joliette,

[52] U.S. Cl. ..34/23, 34/114, 34/155, 226/95 [51] Int. Cl. ..B65b17/28, F26b 13/08 [58] Field of Search ..34/23, 114, 155, 34/160; 226/95[5 6] References Cited UNITED STATES PATENTS 1/1972 Rodwin ..34/1142,777,213 1/1957 Dungler ..34/160 3,316,657 5/1967 Haywood ..34/160 X3,384,973 5/1968 Johansson ..34/23 3,406,464 10/1968 Clark ..34/155 XPrimary Examiner-William F. ODea Assistant ExaminerPeter D. FergusonAttorney-Spencer & Kaye [57] ABSTRACT A web is treated, for exampledried, by passing it around a rotary cylinder, and deflecting it by airpressure, positive and/or suction, applied to the Web immediatelyadjacent the junction of the web and the cylinder to cause the web tocontact a greater portion of the circumferential surface of the cylinderthan it would in the absence of the air pressure.

4 Claims, 8 Drawing Figures PAIENTEDmmze I975 SHEET 1 BF 4 FIG. I.

FIGS.

FIGZ.

PAIENTEDMAY22|975 3 733 711 SHEET 2 OF 4 FIG. 4.

FIG. 5.

PATENTEUHAY 22 I975 SHEET 3 BF 4 FIG. 7.

PATENTEDHAYEZ 0975 3. 733, 711

SHEET l UF 4 APPARATUS FOR AND METHOD OF TREATING A WEB This inventionrelates to apparatus for and a method of treating a web by passing a webaround one or more rotary cylinders.

In papermaking for example, the paper web is passed around one or morerotary cylinders for drying purposes. Usually a drying felt is alsopassed around the drying cylinder, with the paper web between the feltand the cylinder, to press the web against the cylinder to obtain closecontact between the cylinder and the web.

According to this invention, the web is deflected by air pressureapplied immediately adjacent the junction of the web and a cylinder, soas to cause the web to contact a greater portion of the circumferentialsurface of the cylinder than would be the case if the air pressure wasnot applied. The increased contact between the cylinder and the webenables the treatment, for example the drying, to be carried out moreeffectively. In paper drying, the increase in drying efficiency may infact be such that the dryer felt can be omitted.

The air pressure may be applied to the web as it approaches the cylinderand/or as it leaves the cylinder.

The air pressure may be negative, i.e., suction, applied in the throatbetween the web and the cylinder. The suction may be produced by anapropriately shaped foil suitably positioned in the throat, the suctionbeing produced by the air flow around the foil caused by the motion ofthe web and the cylinder. Alternatively, the suction may be produced bya suction bar positioned in the throat, with suction being applied tothe interior of the suction bar from an external source,

'and the suction bar having aperture means directed to wards the web sothat the web is sucked against the cylinder.

Alternatively or additionally, the air pressure may be positive andapplied to the web on the oppposite side thereof to the cylinder. Inthis case, the pressure may be produced by a foil positioned immediatelyadjacent the junction of the web and the cylinder on the opposite sideof the web to the cylinder, the air pressure being produced by the airflow around the foil caused by the motion of the web. Alternatively, theair pressure may be produced by a pressure bar positioned immediatelyadjacent the junction of the web and the cylinder on the opposite sideof the web to the cylinder, the air pressure being supplied to theinterior of the pressure bar from an external source, and the pressurebar having aperture means directed towards the web so that the web isforced by the air pressure into contact with the cylinder.

Both positive air pressure and suction may be applied to the web. Inthis case, the air sucked into the suction bar may subsequently beejected from the pressure bar. The air may be heated before it isejected from the pressure bar to increase the drying efficiency.

The rate of air sucked or blown may be adjustable to vary the tension inthe web and obtain optimum conditions. In particular, the rate of airsucked or blown may be separately adjustable at different positionsalong the width of the web to cater for varying conditions across theweb.

Embodiments of the invention will now be described, by way of example,with reference to the accompanying diagrammatic drawings, of which:

FIG. 1 is a side view of paper drying apparatus using suction,

FIGS. 2 and 3 are side views of part of the apparatus of FIG. 1 showingdifferent suction producing means,

FIG. 4 is a side view of paper drying apparatus using positive airpressure,

FIGS. 5 and 6 are side views of part of the apparatus of FIG. 4 showingdifferent positive air pressure producing means,

FIG. 7 is a side view of paper drying apparatus using suction andpositive air pressure, and

FIG. 8 is a perspective view of paper drying apparatus using suction andair pressure.

Referring first to FIG. 1', the drying section of papermaking apparatusincludes a series of rotary drying cylinders 1 to 5 over which the paperweb 6 successively passes. No drying felt is used. Immediately adjacenteach junction of the web 6 and cylinder (except the first and lastjunctions), suction indicated by arrows S is applied between the web 6and the cylinder to deflect the web into greater contact with thecylinder. The straight path which the web 6 would follow in the absenceof the suction is shown in dotted lines. It will be seen that theapplication of suction causes the web 6 to engage a greater proportionof the circumferential surface of each cylinder than would otherwise bethe case. The amount of suction required for optimum performance in anyparticular set of circumstances can readily be ascertained by routinetrial and experiment.

FIG. 2 shows how the suction can be obtained by appropriately shapedstationary foils 7 positioned between the web 6 and cylinders,immediately adjacent the junctions thereof, and extending across thewidth of the web. The suction is caused by air flow around the foils 7which results from the motion of the cylinders and the web 6.

FIG. 3 shows how the suction can be obtained by suction bars 8positioned between the web 6 and the cylinders, immediately adjacent thejunctions thereof, and extending across the width of the web withaperture means directed towards the web 6. The suction bars 8 areconnected to an external source of suction (not shown) which appliessuction to the interior of the suction bars 8.

FIG. 4 is similar to FIG. 1, but shows the application of positive airpressure, indicated by arrows P, instead of suction, the positive airpressure being applied to the web immediately adjacent its junctionswith the cylinders on the opposite side of the web 6 to the cylinders.FIG. 5 shows the positive air pressure obtained by foils 9 positionedimmediately adjacent the junctions of the web 6 and the cylinders, onthe opposite side of the web 6 to the cylinders. The positive airpressure is produced by the flow of air around the foils 9 caused by themovement of the web 6. FIG. 6 shows the positive air pressure beingobtained by pressure bars 10 which are similar to the suction bars 8,except that they are on the opposite side of the web, and positive airpressure is applied to them.

FIG. 7 is similar to FIGS. 1 and 4, but shows the use of suction andpositive air pressure, the suction being applied as the web 6 contacts acylinder, and the positive air pressure being applied as the web 6leaves a cylinder. Such an arrangement is shown in more detail in FIG.8. The two suction bars 8 shown are connected by ducting 11 to theintake of an air blower 12, whose outlet is connected by ducting 13 tothe two pressure bars shown via a heat exchanger 14 and a dampercontroller 15.

Thus, air sucked into the suction bars 8 is subsequently ejected fromthe pressure bars 10, after first being heated in heat exchanger 14. Hotfluid from any convenient source flows through the heat exchanger 14through lines 16. The damper controller 15 is adjustable to vary therate of air flow in the system. if desired, the suction bars 8 andpressure bars 10 may be equipped with adjustable slides to vary the sizeof the apertures therein differently from place to place across thewidth of the web 6.

It is also possible to apply suction and positive air pressureimmediately adjacent to the samejunction, for example by a suction bar 8on one side of the web and a pressure bar 10 on the opposite side of theweb 6.

Since no drying felt is necessary, all the usual accessories needed fordriving the felt are not required. Also, no pockets are produced betweenthe web and a felt, and consequently pocket ventilators are notrequired. Thus, the drying apparatus is simplified and reduced in cost,and the drying of the web is improved both at different stages in theapparatus and also across the width of the web at any stage.

I claim: s

1. A method of treating a web including passing the web around a rotarycylinder, and deflecting the web by air pressure applied to the webimmediately adjacent the junction of the web and the cylinder to causethe web to contact a greater portion of the circumferential surface ofthe cylinder than it would in the absence of the air pressure, the airpressure being suction applied between the web and the cylinder andpositive air pressure applied on the opposite side of the web to thecylinder.

2. A method according to claim 1 wherein the positive air pressure isair from the suction subsequently pressurized.

3. A method according to claim 1 wherein the web is a paper web and thecylinder is a drying cylinder.

4. Apparatus for treating a web including a rotary cylinder around whichthe web is passed, and means for applying air pressure to the webimmediately adjacent the junction of the web and the cylinder to deflectthe web and cuase the web to contact a greater portion of thecircumferential surface of the cylinder than it would in the absence ofthe air pressure, the pressure applying means applying suction betweenthe web and the cylinder and applying positive air pressure to the webon the opposite side thereof to the cylinder.

1. A method of treating a web including passing the web around a rotarycylinder, and deflecting the web by air pressure applied to the webimmediately adjacent the junction of the web and the cylinder to causethe web to contact a greater portion of the circumferential surface ofthe cylinder than it would in the absence of the air pressure, the airpressure being suction applied between the web and the cylinder andpositive air pressure applied on the opposite side of the web to thecylinder.
 2. A method according to claim 1 wherein the positive airpressure is air from the suction subsequently pressurized.
 3. A methodaccording to claim 1 wherein the web is a paper web and the cylinder isa drying cylinder.
 4. Apparatus for treating a web including a rotarycylinder around which the web is passed, and means for applying airpressure to the web immediately adjacent the junction of the web and thecylinder to deflect the web and cuase the web to contact a greaterportion of the circumferential surface of the cylinder than it would inthe absence of the air pressure, the pressure applying means applyingsuction between the web and the cylinder and applying positive airpressure to the web on the opposite side thereof to the cylinder.